This disclosure relates to power converters capable of providing multiple output voltage levels. With respect to USB-C adapter design, the converter's output may need to be changed between different voltage levels, e.g., a low voltage (such as 5V, 10V), an intermediate voltage (such as 12V, 20V), or a high voltage (such as 20V, 40V)—based on the charging device's request. By using a tapped-winding transformer, the turns-ratio of a flyback transformer may be intelligently selected for high output voltage ranges, thus enabling the duty cycle to be kept the same for the low and intermediate voltage output levels. The flyback converter would then only need to accommodate the intermediate and high output voltages. For high output voltages, a switch may be activated to put the two windings of the transformer in series; for lower output voltages, the switch may be turned off, such that only one winding is used.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A power conversion apparatus comprising: a transformer, wherein the transformer has a primary winding and a tapped secondary winding having a first number of turns and a second number of turns, wherein the first number of turns is less than a total number of turns of the secondary winding of the transformer and wherein the second number of turns is larger than the first number of turns of the secondary winding of the transformer; a first switch coupled to the primary winding so as to control a flow of current through the primary winding; a second switch coupled in series between the secondary winding and ground; and circuitry coupled to the first switch and the second switch, configured to: switch the first switch using a first duty cycle and turn the second switch off, so as to allow current to flow through the first number of turns of the secondary winding of the transformer, thereby outputting a low voltage; switch the first switch using the first duty cycle and turn the second switch on, so as to allow current to flow through a second number of turns of the secondary winding of the transformer, thereby outputting an intermediate voltage; and switch the first switch using a second duty cycle and turn the second switch on, so as to allow current to flow through the second number of turns of the secondary winding of the transformer, thereby outputting a high voltage.
2. The apparatus of claim 1 , further comprising a synchronous rectifier (SR) circuit.
3. The apparatus of claim 2 , comprising a first synchronous rectifier coupled to the first number of turns of the secondary winding and a second synchronous rectifier coupled to the second number of turns of the secondary winding.
4. The apparatus of claim 1 , wherein the low voltage is 5V, the intermediate voltage is 12V, and the high voltage is 20V.
5. The apparatus of claim 1 , wherein a ratio of the first number of turns to the second number of turns is 5:12.
6. The apparatus of claim 1 , further comprising a third switch configured to disconnect the output side of the power conversion apparatus under abnormal conditions.
7. The apparatus of claim 1 , wherein the second switch comprises an N-FET or a P-FET.
8. The apparatus of claim 1 , wherein the second number of turns of the secondary winding is equal to the total number of turns of the secondary winding.
9. The apparatus of claim 1 , wherein the output voltage produced by the power conversion apparatus is determined based on a requirement of a device that power is being delivered to.
10. The apparatus of claim 9 , wherein the power conversion apparatus is configured to deliver power over a USB-C cable.
11. A power circuit comprising: a transformer configured to store energy and output a plurality of output voltage levels, the transformer including a primary side winding and a secondary side winding; a first switching device arranged in series with the primary side winding of the transformer, so as to change a duty cycle of the primary side winding from producing the low or intermediate output voltage to producing the high output voltage; a second switching device arranged in series between the secondary side winding of the transformer and ground so as to use a different number of turns of the secondary side winding to produce a low output voltage and an intermediate or high output voltage, respectively.
12. The power circuit of claim 11 , further comprising a third switching device coupled in series with a portion of the secondary side winding and configured to operate as a synchronous rectifier when producing the low output voltage.
13. The power circuit of claim 11 , further comprising a fourth switching device coupled in series with the secondary side winding and the second switching device and configured to operate as a synchronous rectifier when producing the intermediate and high output voltages.
14. A power converter comprising: a transformer having a primary winding and a secondary winding having a tap; a first switch coupled in series with the primary winding to control a flow of current through the primary winding; a second switch coupled to the tap of the secondary winding so as to be in series with a first portion of the secondary winding; a third switch and a fourth switch coupled in series with each other and in series with an entirety of the secondary winding; and circuitry coupled to the first switch and the fourth switch, configured to: switch the first switch using a first duty cycle and turn the fourth switch off, so as to allow current to flow through the first portion of the secondary winding of the transformer, and using the second switch as a synchronous rectifier, thereby outputting a low voltage; switch the first switch using the first duty cycle and turn the fourth switch on, so as to allow current to flow through the entirety of the secondary winding of the transformer, and using the second switch as a synchronous rectifier, thereby outputting an intermediate voltage; and switch the first switch using a second duty cycle and turn the fourth switch on, so as to allow current to flow through the entirety of the secondary winding of the transformer, and using the second switch as a synchronous rectifier, thereby outputting a high voltage.
15. The power converter of claim 14 , wherein the low voltage is 5V, the intermediate voltage is 12V, and the high voltage is 20V.
16. The power converter of claim 14 , wherein a ratio of a number of turns in the first portion of the secondary winding to a number of turns in the entirety of the secondary winding is 5:12.
17. The power converter of claim 14 , further comprising a third switch configured to disconnect the output side of the power conversion apparatus under abnormal conditions.
18. The power converter of claim 14 , wherein the output voltage produced by the power conversion apparatus is determined based on a requirement of a device that power is being delivered to.
19. The power converter of claim 14 , wherein the power conversion apparatus is configured to deliver power over a USB-C cable.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
July 1, 2016
April 9, 2019
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